1. Field of the Invention
The present invention relates to a sensor device, in which a sensing element is exposed and a connecting portion between a wiring portion and a lead is covered with a molded member, and a method for manufacturing the same.
2. Description of Related Arts
U.S. Pat. No. 5,396,795 (corresponding to JP-B2-2784286) discloses a manufacturing method of a sensor device in which a sensing element is exposed and a connecting portion between a wiring portion and a lead is covered with a molded member.
In the method according to the U.S. Pat. No. 5,396,795, firstly a dam resin membrane made of silicon resin is formed around a sensor element portion. Secondly, only a connecting portion between a connecting terminal and a lead is covered with a molded resin, while the sensor element is exposed. The molded resin sandwiches a semiconductor chip through the dam resin membrane so that the dam resin membrane plays a role of a shield. That is, the sensor element portion can be prevented from being contaminated by the molded resin.
Also, Japanese Patent No. 3,328,547 discloses a thermal type flow sensor. In the flow sensor, a flow-detecting chip is mounted to a supporting member. A part of a flow-detecting portion including a heater is exposed to a fluid to be measured. An area including a connecting portion and a circuit chip is covered with a molded member integrally. The connecting portion connects a connecting wire to the flow-detecting portion, a circuit portion, and a lead.
In the above-described thermal type flow sensor, the supporting member includes an end face and both side faces for positioning of the flow-detecting chip. The faces of the supporting member are bent in a vertical direction from a bottom part of the supporting member, in which the flow-detecting chip is disposed. The position of the flow-detecting chip is determined by the end face and the both side faces of the supporting member. The flow-detecting chip is disposed in the supporting member to cover a cavity portion underneath a membrane portion of a substrate. Therefore, the cavity portion underneath the membrane portion of the flow detection chip is covered with the supporting member. Thus, the cavity is not directory exposed to the fluid, i.e., air to be measured. Accordingly, a generation of a turbulent at the cavity portion can be prevented. A temperature fluctuation of the heater can be decreased so that a noise of an output signal can be decreased.
However, according to the manufacturing method of the sensor device shown in U.S. Pat. No. 5,396,795, a burr may be formed in the side faces of the semiconductor chip because the dam resin membrane cannot be provided on the side faces of the semiconductor chip.
For example, if the manufacturing method shown in U.S. Pat. No. 5,396,795 is simply applied to the thermal type flow sensor according to Japanese Patent No. 3,328,547, a burr may be formed in the side faces of the flow-detecting chip, because there is a clearance between the side face of the supporting member and the side face of the flow-detecting chip. The molding material can pass through the clearance at the mold forming time. In this case, if a burr is formed, a turbulent may be generated by the burr. Thus, an accuracy of detection cannot be maintained.